In the past, gyroscopes and gyroscopic devices were constructed of relatively large and expensive electromagnetic devices. These electromagnetic devices incorporated coils and position sensors mounted for relatively high speed, continuous rotational movement.
Eventually, micromechanical rate gyros were developed which included components formed by semiconductor processing techniques. While these devices are relatively small and utilize vibrational motion rather than continuous rotary motion, they are relatively insensitive and costly to manufacture.
Generally, the micromechanical rate gyros are constructed with a central mass, which because of the size of the gyro is very small and requires some very heavy material such as gold to provide sufficient inertia to meet the sensitivity requirements. The central mass is mounted in a gimbal structure including mutually orthogonal flexible axes, with the mass and gimbal structure generally lying in a common plane. The central mass and inner mounting gimbal are oscillated or vibrated about a first of the orthogonal axes and rotational movement about an axis perpendicular to the common plane produces vibrational movement about the other of the orthogonal axes, due to the Coriolis, or gyroscopic, effect.
The described micromechanical rate gyro has several problems. Specifically, the centrally mounted mass is expensive and difficult to manufacture. Second, the amount of mass is limited by the fact that it is centrally mounted in a planar constructed gimbal system which substantially reduces the momentum of the mass and, therefore, produces a very small torque, or moment, about the driven axis. Also, because of the central mounting of the mass in a gimbal system a greater amount of mass and actual vibratory movement of the mass is required to produce a desired sensitivity.
To further reduce the size, cost and usefulness of rate gyros, there is a need for micromechanical rate gyros with increased sensitivity.